1. Field of the Invention
The present invention relates to a wiring board and its manufacturing method.
2. Discussion of the Background
In recent years, as various semiconductor elements have become highly integrated and have even more pins, printed wiring boards that have finer wiring are being required. Accordingly, demand is increasing for multilayer printed wiring boards having finer conductive wirings on both their inside and outside. In addition, since analog signals and digital-pulse signals are used in electronic devices in which printed wiring boards are used, arrangements similar to those for alternating-current signals are required. In such a multilayer printed wiring board, when alternating-current signals flow, impedance (inductance) rises in a through-hole conductor to be used as a power-supply line to a CPU. Accordingly, if a sudden demand for power comes from the CPU, the supply of voltage may be delayed and thus may pose an obstacle to the operation of the CPU.
In Japanese Laid-Open Patent Publication No. 2002-204075, a printed wiring board is described where through holes with a coaxial structure are used. In the present application, the contents of Japanese Laid-Open Patent Application No. 2002-204075 are incorporated herein by reference in their entirety.